Control system



p R. w. GEMMELL 2,053,428

' CONTROL SYSTEM F-iled'June '15, 1935 $abcd li'i l l l l l l'l lWITNESSES: INVENTOR (2'. 4 VJ v EOberf/L Gemme/Z /7 w/ 5 Patented Sept.8, 1936 UNITED STATES CONTROL SYSTEM Robert W. Gemmell, Pittsburgh, Pa.,assignor to Westinghouse Electric & Manufacturing Company, EastPittsburgh, Pa., a corporation of Pennsylvania Application June 15,

9 Claims.

My invention relates, generally, to control systems and moreparticularly to systems for regulating the operation of internalcombustion engines which are utilized to drive electric generators.

Numerous schemes have been proposed and utilized for regulating thespeed of an internal combustion engine, which drives a generator, by socontrolling the torque requirements of the generator that a practicallyconstant engine speed is maintained. In the prior schemes, an indicationof a change in the speed of the engine is obtained by utilizing thevoltage of either a pilot generator or an auxiliary generator or exciterfor the main generator of the power system, all of which are driven bythe engine. Since the voltage of the pilot generator or the exciter isapproximately proportional to the engine speed, it is used to operatethe regulating element for the powers system.

However, in such a system it is necessary to provide a separate pilotgenerator, which entails additional expense, or to utilize the voltageof the auxiliary generator or exciter as an indication of the enginespeed. The latter method hasnot proven entirely satisfactory in allcases, especially where the auxiliary generator is subjected to highlyfluctuating loads, as, for example when the auxiliary generator suppliesthe excitatid n current for the main generator of a Diesel-electriclocomotive and also supplies current for operating the air conditioningequipment for the train being hauled by the locomotive. The loadfluctuations produce variations in the-generator voltage which causeerratic operation of the system for regulating the speed of the engine.

An object of my invention, generally stated, is to provide a controlsystem for regulating the speed of an internal combustion engine whichshall be simple and. eiiicient in operation and "which may beeconomically manufactured and installed.

A more specific object of my invention is to provide a system forregulating the speed of an internal combustion engine which is directlyresponsive to the speed of the engine.

Another object of my invention is to provide a system for regulating thespeed of an internal combustion engine which is not affected byfluctuations in the load on the generating apparatus driven by theengine.

A further object of my invention is to prevent hunting or surging of aspeed regulating system.

Other objects of my invention will be explained 1935, Serial No. 26,840-

fully hereinafter or will be apparent to those skilled in the art.

In accordance with the preferred embodiment of my invention, an internalcombustion engine is utilized for driving a main generator to generatecurrent for operating the propelling motors of a locomotive and also anauxiliary generator which supplies excitation current for the maingenerator. .A speed regulator of the magnetic drag type, which is drivenby the engine shaft, and is, therefore, directly responsive to the speedof the engine, is provided for controlling the excitation current of themain generator, thereby controlling the load and the torque requirementsof the main generator to regulate the speed of the engine.

For a fuller understanding of the nature and objects of my invention,reference may be had to the following detailed description, taken inconjunction with the accompanying drawing, in which:

Figure 1 is a diagrammatic view of a control system embodying myinvention;

Fig. 2 is a view, in section, taken along the line II'II of Fig. 3, of arelay of the magnetic drag type, which is utilized in the controlsystem; and

Fig. 3 is a View, in section, of the relay shown in Fig. 2. 7

Referring to the drawing, and particularly to Fig. Lian internalcombustion engine ill is utilized for driving an electric generator H.The generator I l supplies the current for operating an electric motorl2, which may be of a type suitable for propelling a locomotive (notshown). A reversing switch i3 is provided for reversing the current inthe field winding I l of the motor l2, thereby controlling the directionof rotation of the motor. An auxiliary generator or exciter i5 isprovided for energizing the field winding I6 of the main generator H.The exciter l5 may be of the shunt wound type having a shunt fieldwinding ii.

In order that the excitation current of the main generator H may bevaried, a resistor I8 is connected in series with the field winding itof the generator l l, and a resistor shunting switch i9 isprovided forshunting the resistor I8 from the field winding circuit. It will beunderstood that when the contact members 2| of the switch B9 are closedto shunt the resistor 18, a maximum amount of excitation current issupplied the generator H by the exciter l5. Also, when the contactmembers 2| oi the switch l9 are opened to insert the resistor I8 in thefield winding circuit,

. a minimum amount of excitation current is supplied the generator ll.

, carried by the generator and consequently the torque required to drivethe generator. Therefore, the speed of the engine In may be regulated byvarying the torque requirements of the generator I I. Thus, the speed ofthe engine may be increased by decreasing the excitation current ofthe-generator H, and, likewise, the speed of the engine may be decreasedby increasing the excitation current to increase the load carried by thegenerator it.

In order that variations in the speed of the engine l0 may be utilizedto control the operation of the resistor shunting switch it to vary theexcitation current of the generator H, in the manner hereinbeforedescribed, a speed regulating relay 23 is connected to the engine shaft2 thereby being mechanically driven by the engine. The relay 23 is ofthe magnetic drag type and is more fully described in the copendingapplication of W. R. Taliaferro, Serial No. 17,969, filed April 24,1935. a

As shown in Figs. 2 and 3, the relay 23 com prises a rotating magnet 25,which is driven by the engine shaft 2 The magnet 25 is concentricallydisposed within a rotatable cup 26, which may be composed of copper orother suitable non-magnetic material. The cup 26 is carried by a shaft21, which is supported by bearings 28 and 29 m'ounted in a framework 3!.A laminated ring 32 is supported by the frame 3! and surrounds themagnet 25 and the cup 26, thereby providing a magnetic path for the fluxproduced by the magnet 25.

In this manner, a magnetic drag or torque is produced on the cup 2% bythe rotating magnet 25 which is proportional to the speed of rotation ofthe magnet 25 and the speed of the engine it, since the magnet 25 isdriven by the engine shaft 25. The rotation of the cup 25 is opposed byan adjustable spring disposed to bias a contact block 36, which ismounted on the shaft 21 of .the cup 26, to a predetermined position.Contact members 35 and 3B are carried by the contact block 36, as shownin Fig. l-,I and are disposed to engage contact members Q'i'and 38,respectively, when the torque developed by the rotating magnet 25 issufilcient to overcome the tension of the spring 33. In this manner, therelay 23 is so constructed that it is directly responsive to the speedof the engine it and the relay may be utilized to control theenerglzation of the actuating coil 39 of the resistor shunting switchl9, thereby controlling the generator excitation current and regulatingthe speed of the engine Hi.

It will also be understood that, if desired, the contact members of therelay 23 may be directly utilized to shunt the resistor 88, therebyvarying the excitation current of the generator l l to regulatetheengine speed without providing the resistor shunting switch l9. However,when controlling a generator of a comparatively large size,

aosaaae it will be found expedient to utilize a separate resistorshunting switch, as herein illustrated.

In order to obtain a plurality of difierent speed settings for the relay23, a solenoid ll, which is energized by a coil 42, maybe so connectedto the relay that it opposes the action of the spring 33. The coil 52may be energized from a control battery 433, or other suitable source ofcontrol potential. The current in the coil t2 may be controlled by meansor" a resistor 44, which may be shunted step-by-step from the circuitthrough the coil by means of a control switch d of the drum type.

In order tn reduce the hunting or surging action of the regulatingsystem, provision is made for shunting a portion 56 of the solenoid coil42 by means at the contact members 36 and 38 of the relay 23, when thesecontact members are closed by the torque produced by the rotating magnet25. The relay is so constructed and connected in the regulating systemthat its contact members are closed when the engine attains a speedwhich causes suficient torque to-be developed in the relay 23 toovercome the spring 33. The coil 62 opposes the spring 33, therebyaiding the relay torque to close the contact members. Since the shuntingof a portion of the coil t2 reduces the magnetic efiect of the coil thespring 33 is enabled to open the contact members of the relay slightlybefore the engine has decreased to the speed otherwise permitted by therelay 23. In this manner, overshooting of the engine speed is preventedwhich reduces the hunting or surging action usually experienced in speedregulating systems.

If desired, a further means of preventing hunting may be provided byadding an additional coil ti on the solenoid ll to increase the effectof the solenoid in opposing the spring 33. As shown, the coil All may beconnectedin parallel with the resistor l8, thereby being shunted by theclosing of the contact members H of the resistor shunting switch l9.Since the shunting of the resistor It by the contact members Zlincreases the excitation current of the generator l I and decreases theengine speed, in the manner hereinbefore described, the shunting of thecoil ll simultaneously with the resistor It permits the spring 33 toopen the contact members of the relay 23 before the engine has decreasedto its minimum speed permitted by the normal setting of the relay 23.Likewise, the coil il prevents overshooting when the engine speed isbeing increased by the relay 23, since the coil dl is energized at thistime and it will cause the contact members of the relay 23 to be closedslightly before the maximum speed of the engine is attained.

As shown, the battery $3 is utilized to supply current for operating thecontrol apparatus, such as the resistor shunting switch i9 and thesolenoid device ll. The exciter or auxiliary generator it may beutilized to charge the battery 63 by closing a switch 68 to connect thebattery d3 across the generator l5.

In order that the functioning of the foregoing apparatus may be moreclearly understood, the operation of the control system will now bebriefly described. Assuming that the engine It is driving the generatorl l and that the engine throttle (not shown) has been so set that theengine l0 may operate at a desired speed, the regulating systemhereinbefore described will function to maintain the desired speed ofthe engine it) by controlling the excitation current of the gener- Asshown, when the control switch 45 is in position a, the entire resistor44 is shunted from the circuit of the coil 42 and the solenoid 4| hasits maximum efiect. Therefore, the engine Ill will operate at itsmlnimumspeed for a predetermined throttle opening. By inserting the resistor 44in the circuit of the coil 42 stepby-step, the efiect of the solenoid 4|is decreased,

' which increases the engine speed since more torque is required in therelay 23 to overcome the spring 33. When the controller is in the ofif?position the engine throttle is set for idling speed and no regulationis required.

When the engine l0 attains a predetermined speed, the contact members 35and 31 of the relay 23 are closed. by the torque produced by therotating magnet 25, thereby energizing the actuating coil 39 of theresistor shunting switch l9, which closes the contact members 2| oi thisswitch to shunt the resistor l8 from the circuit of the field winding l5of the generator II. The energizing circuit for the actuating coil ofswitch l9 extends from the positive terminal of the battery 43 throughconductors 5| and 52, the coil 39, conductor 53, contact members 35 and31 of the relay 23, and conductors 54 and to the negative terminal ofthe battery 43.

As hereinbefore described, the shunting of the resistor I8 increases theexcitation current of the generator I I, thereby increasing the loadcarried by the generator and increasing the torque on the engine l0,which will decrease the engine speed for a fixed throttle setting. Whenthe engine speed is reduced a suificient, amount to permit the spring 33to open the contact members of the relay 23, the resistor shuntingswitch is opened and the resistor I8 is inserted in the field windingcircuit to decrease the torque requirements of the generator H, whichpermits the previously known systems for regulating the speed ofinternalcombustion engines, which are utilized for driving thegenerators of Diesel-electric or gas-electric locomotives. As statedhereinbefore, previously known regulating systems have either requiredan independent pilot generator for operating the regulating equipment,or have been subject to fluctuations in the electrical load imposed onthe generating equipment of the power system, which causes erraticoperation of the regulating system.

The system herein described is directly responsive to the speed of theengine l0, and is not affected by any fluctuations in the load which maybe imposed on the generator 15 by such auxiliary equipment asair-compressor motors, battery charging and'the air conditioningequipment utilized on modern trains.

I do not desire to be restricted to the specific embodiment of myinvention herein shown and described, since it is evident that it may bechanged and modified without departing from I the spirit and scope of myinvention as defined in the appended claims.

I claim as my invention: 1. In a power system, in combination, anelectric generator, an internal combustion engine for driving thegenerator, a source of direct current for exciting the generator, meansdirectly responsive to the speed of the engine for controlling thegenerator excitation current to vary the torque of the'generator,thereby regulating the speed of the engine, and electroresponsive meansfor reducing hunting of said speed-responsive means.

2. In a power system, in combination, an electric generator, an internalcombustion engine for driving the generator, 9. source of direct currentfor exciting the generator, means mechanically driven by the engine .anddirectly responsive to its speed for controlling the generatorexcitation current to vary the torque of the generator, therebyregulating the speed of the engine, and electro-responsive means forreducing hunting of said speed-responsive means.

3. In a' power system, in combination, an electric generator, aninternal combustion engine for driving the generator, a source of directcurrent for exciting the generator, means for varying the generatorexcitation current to control the generator torque, means directlyresponsive to the engine speed for controlling the operation of saidlast named means, thereby regulating the speed of the engine, andelectro-responsive means for reducing hunting of said speed-responsivemeans.

4. In a power system, in combination, an electric generator, an internalcombustion engine for driving the generator, a source of direct currentfor exciting the generator, a resistor for controlling the generatorexcitation current, means for shunting said resistor to control thegenerator torque, and means mechanically driven by the engine anddirectly responsive to the engine speed for controlling the operation ofsaid resistor shunting means, thereby regulating the speed of theengine, and electro-responsive means for reducing hunting of saidspeed-responsive means.

5. In a power system, in combination, an electric generator having afield winding, an excit er for energizing the field winding, an internalcombustion engine for driving the generator and the exciter, a speedregulator for controlling the energization of said generator fieldwinding, said speed regulator having a rotating magnet driven by theengine and a rotatable member actuated by the rotating magnet to efiectthe control or the generator excitation current, and electro-responsivemeans for changing the speed I setting of said regulator.

6. In a power system, in combination, an electric generator havingafield winding, an internal combustion engine for driving the generator,means for supplying excitation current for the generator field winding,a speed regulator for controlling said excitation current to vary thegenerator torque, said regulator having a rotating magnet driven by theengine, a rotatable member disposed concentric with the rotating magnetand actuated thereby in accordance with the speed of the engine, andremotely controlled electro-responsive means for changing the speedsetting of said regulator.

7. In a power system, in combination, an electric generator having afield winding, an intergenerator torque, said regulator having a rotat-I able member, a rotating magnet driven by the engine and concentricallydisposed within the rotating member to produce a torque thereonproportional to the engine speed, a spring for biasing the rotatablemember to a predetermined position, electro-responsive means forchanging the speed setting of said regulator, and means for remotelycontrolling the energization of said electro-responsive means.

8. In a power system, in combination, an electric generator having afield winding, an internal combustion engine for driving the generator,means for supplying excitation current for the generator field winding,a speed regulator for controlling said excitation current to vary thegenerator torque, said regulator having a rotatable member, a rotatingmagnet driven, by the engine and concentrically disposed within therotating member to produce a torque thereon proportional to the enginespeed, a spring for biasing the rotatable member to a predeterminedposition, and electro-responsive meansdisposed to oppose said spring toreduce hunting of theregulator.

9. In a power system, in combination, an electric generator having afield winding, an internal combustion engine for driving the generator,means for supplying excitation current for the generator field winding,a speed regulator for controlling said excitation current to vary thegenerator torque, said regulator having a rotatable member, a rotatingmagnet driven by the.

engine and concentrically disposed within the rotatingmember to producea torque thereon proportional to the engine speed, a spring for biasingthe rotatable member to a predetermined position, electro-responsivemeans disposedto oppose said spring to reduce hunting of the regulator,and contact members actuated by the rotatable member of said regulatorto control the energization of said electro-responsive means.

ROBERT W. GEMMELL.

